bitrotate: better 'inline' * lib/bitrotate.c: New file. * lib/bitrotate.h (BITROTATE_INLINE): New macros. Replace all uses of 'static inline' with them. Use _GL_INLINE_HEADER_BEGIN, _GL_INLINE_HEADER_END. * modules/bitrotate (Files, lib_SOURCES): Add lib/bitrotate.c. (Depends-on): Add extern-inline. (configure.ac): Do not require AC_C_INLINE.